Prelaminate pressure-sensitive adhesive constructions

ABSTRACT

Prelaminate pressure-sensitive adhesive (PSA) constructions comprise, a first substrate, a coating or release material on a surface of the first substrate, a PSA layer disposed on the coating of release material, and a detackified layer (DL) disposed on a surface of the PSA layer to form a continuous film covering the PSA layer. In first and second embodiments of the construction the DL is activatable to form a tacky layer on top of the PSA layer for lamination with a second substrate. In a third embodiment, the DL includes constituents that when activated migrate into the PSA layer to expose the PSA layer tacky surface for lamination with a second substrate. The prelaminate PSA constructions are completely nonblocking to a minimum 24 hour blocking temperature of about 50° C. at pressure of about 40 kilopascals, thereby allowing such prelaminate PSA construction to be collected, stored, and or transported before being laminated without adhesive interference occurring between continuous layers. The DL in each embodiment is activatable in less than five seconds to provide a tacky layer having a sufficient open tack time to permit lamination at less than about 100° C.

RELATION TO COPENDING PATENT APPLICATION

This patent application is a Divisional of U.S. patent application Ser.No. 10/353,294 filed on Jan. 28, 2003, which was a Continuation of U.S.patent application Ser. No. 09/587,915 filed on Jun. 6, 2002 and thatissued as U.S. Pat. No. 6,540,865 on Apr. 1, 2003, which was aDivisional of U.S. patent application Ser. No. 08/999,525 filed on Sep.26, 1997, which claimed priority from U.S. Provisional PatentApplication Ser. No. 60/026,819 filed on Sep. 27, 1996.

FIELD OF THE INVENTION

The present invention relates to pressure-sensitive adhesiveconstructions and methods for making the same and, more particularly, toprelaminate pressure-sensitive adhesive constructions having adetackified surface to provide anti-blocking characteristics forfacilitating subsequent handling and/or treatment of the constructionbefore lamination to a second substrate.

BACKGROUND OF THE INVENTION

Pressure-sensitive adhesive (PSA) constructions such as labels, tapes,decals and the like are known in the art. For example, PSA labelconstructions are commonly used to apply a particular face stock havinga specific nature of printing to an object or article, and areespecially useful where objects having low surface energies are to belabeled. PSA label constructions typically comprise a face stock, aliner, and a PSA layer interposed between the face stock and liner.

In accordance with well known practice in the industry, the liner may becoated with a releasable material, forming a release liner. Thereleasable surface of the release liner may be coated with a layer ofPSA for subsequent transfer of the adhesive to the face stock with whichthe release liner is employed. When the face stock is combined with therelease liner, the adhesive is laminated to the face stock.Alternatively, the adhesive may have been directly coated on or combinedwith the face stock prior to combining the face stock with the releaseliner. In either approach, in a later step the release liner is removedfrom the PSA and face stock construction to expose the adhesive, whichremains permanently joined to the face stock.

Thus, as indicated in FIG. 1, a PSA 10 may be applied to the releasesurface of the release liner 12 at a station 14 following drying orcuring of a release coat 16 previously applied to the release liner atstation 18. This may be a tandem coating operation, or the adhesivecoating 10 may be applied on a separate coating line. The PSA may beformed from a material that requires drying before application of theface stock, in which case the face stock is applied to the dried PSAlayer. In some cases the release surface 16 is precoated onto therelease liner 12, and the adhesive 10 is applied at a later time priorto laminating the release liner 12 to a face stock 20. The combining ofthe release liner and face stock is diagrammatically illustrated in FIG.2.

Most commonly, the resulting laminated construction takes the form of acontinuous ribbon or web that is collected on a roll. This roll may betransported to a converter for further operations such as printing, diecutting, and matrix stripping, in order to create labels, signs, orother PSA products. Thus for example, FIG. 3 illustrates the die cuttingof the face stock 20 at a station 22 into a series of PSA labels 24 ofdesired shape and size, carried by the release liner 12.

The manufacturing processes described above share the characteristicthat the lamination of the release liner, PSA, and face stock occur at acommon production facility. To promote flexibility in the production ofPSA constructions, it is desired to devise a method for coating therelease liner with a PSA (thereby forming a “prelaminate construction”)in a separate and independent operation from laminating the prelaminateconstruction to face stock. These operations should be capable, forexample, of allowing the prelaminate construction to be produced at adifferent geographic location, or in a separate and independentproduction line, than that at which the prelaminate construction islaminated to the face stock.

One way in which this desire has been addressed has been to make PSAconstructions having a subsequent layer of material applied to theexposed surface of the adhesive in an effort to detackify the adhesivesurface. Detackifying the PSA construction in such manner has beenthought to be an effective way of forming a nonblocking PSA constructionthat, in theory, would permit the prelaminate PSA construction to berolled upon itself and stored or transported for subsequent laminationwithout adhering to a backside surface of the construction, or toanything else. In practice, however, detackified PSA constructions knownin the art have not been entirely effective at providing a completelynonblocking construction.

As used herein, the term “nonblocking” is intended to mean that theprelaminate PSA construction is capable of preventing any significantbonding or adhering to contiguous layers of the label construction,i.e., the backside surface of the release liner, during storage,transportation and handling of the construction so that the removal orseparation of the prelaminate PSA construction from contiguous layers ofthe construction, when collected and/or stored in sheet or roll form,will not be impaired.

For example, U.S. Pat. No. 4,135,033 discloses a two-layer adhesivecoating having a dry, nontacky surface that is convertible to apermanently adhesive surface by application of heat over a period of tenseconds. The two-layer adhesive coating can be used with siliconetreated release paper. In manufacturing PSA constructions it is desiredthat the step of heating and laminating the PSA construction becompleted quickly to maximize the web speed and, thereby maximizemanufacturing efficiency. The need to heat activate such nontackysurface over the relatively long period of ten seconds is contrary tothe goal of achieving manufacturing efficiency, and thus is noteconomically practical.

Additionally, in practice it is known that the patented two-layeradhesive coating is not effective at forming a completely nonblockingPSA construction, thereby permitting adhesional interference to occurbetween contiguous PSA construction surfaces. Such blocking is believedto be caused by the failure of nontacky surface to form a completelycontinuous film to cover the underlying adhesive layer.

U.S. Pat. No. 3,843,480 discloses a process for preparing asurface-detack layer on a PSA that is carried releasably upon asupporting release liner. The process includes the steps of applying aPSA layer onto a release liner and dusting a surface portion of the PSAlayer with a mineral powder to detackify the PSA layer. The resultingdetackified PSA layer is said to permit the prelaminate construction tobe wound upon itself or sheeted and stacked without adhesionalinterference. However, in practice it is known that such patentedprelaminate constructions are not completely effective at preventingblocking, as adhesional interference between contiguous constructionlayers is known to occur. A reason for such blocking is believed to bethe failure of the mineral powder to form a continuous PSA coveringfilm.

The surface detack layer of such patented construction is subsequentlyattached to another substrate surface, such as printing paper and thelike, by a single process step of simultaneously heating the surface ofboth the detack layer and the printing paper, while applying pressure tothe printing paper and heated detack layer to form a completed laminateconstruction.

Simultaneous heat activation of the detack layer and pressurelamination, however, is problematic because it limits the types ofsubstrate materials that can be used. For example, thermally-sensitivesubstrates such as thermal print paper, films of polymers having a lowglass transition temperature, and oriented polymer films cannot be usedwith this process because the step of heating such substrates is knownto adversely impact the desired performance of these materials.

The need to simultaneously heat activate and laminate the PSAconstruction is also not desired because of the related problems thatare known to occur at the nip, such as wrinkling and buckling of thelaminated construction that is caused by the different coefficients ofexpansion between the prelaminate PSA construction and the laminatedsubstrate. Additionally, simultaneous heat activation and lamination isalso known to cause shrinkage in paper face stocks due to the loss ofwater that occurs during such heat exposure, which is known to causecurling and the like. Simultaneous heat activation and lamination canalso cause the outgassing of steam or other vapors in the nip, which isknown to result in bubble formation at the nip and produce a laminateconstruction having areas of poor anchorage.

U.S. Pat. No. 3,343,978 discloses an adhesive structure comprising aflexible substrate, a PSA in contact with the substrate, and a nontackylayer adhering to the surface of the PSA. The nontacky layer can beformed from a material that is subsequently heat activated to form asecond tacky layer, which is simultaneously heat laminated to a desiredfirst article. The flexible substrate is removed to expose the PSA,which is placed into contact with a desired second article.

Again, the need to heat laminate the first article to an activated tackylayer, when using a heat activatable nontacky layer, limits the types offirst articles capable of being used with the adhesive structure tothose that are not affected by exposure to high temperatures, andintroduces the numerous problems described above that are encounteredduring heated lamination.

U.S. Pat. No. 3,027,271 discloses a PSA composite comprising a facestock, a PSA tacky layer deposited onto the surface of the face stock,and a dry powder layer deposited onto the surface of the PSA tackylayer. The dry powder is intended to detackify the underlying PSA tackylayer and, in theory, allow the face stock material to be stored orstacked without sticking to itself. The dry powder layer is formed fromdry particles that are removable upon application of heat byvaporization or decomposition into gaseous products, thereby exposingthe underlying tacky layer for application of the composite at the pointof use.

As discussed above with reference to the construction described in U.S.Pat. No. 3,843,480, the use of a dry powder in this patented compositealso fails to provide a completely nonblocking PSA composite, therebypermitting adhesional interference to occur between contiguous surfacesof the PSA composite. The reason for this is believed to be the failureof the dry powder layer to form a continuous PSA covering film.

Having to heat the composite to remove or vaporize the dry powder layerand expose the PSA tacky layer, again limits the type of face stocksthat can be used to form the composite to those not affected by exposureto high temperatures. Additionally, the patented composite that isdisclosed is one that includes a face stock and, therefore, does notaddress the desire to provide a face stock-free prelaminate PSAconstruction.

It is, therefore, desired that prelaminate PSA constructions be designedand manufactured to have nonblocking properties enabling suchprelaminate PSA constructions to be collected in roll form or the likeand stored without adhering to contiguous layers for subsequentlamination to a substrate It is desired that prelaminate PSAconstructions be capable of being activated in a relatively short amountof time prior to lamination with a substrate to maximize manufacturingefficiency. It is also desired that prelaminate PSA constructions becapable of facilitating lamination at temperature conditions that do notlimit the types of laminating substrate that can be used, and that avoidproblems known to occur during heated lamination. It is further desiredthat the prelaminate PSA construction be capable of facilitatinglamination without the emission or use of potentially dangerous orharmful gases or chemicals.

Additionally, it is desired to provide a process for adhesivelyactivating and later laminating a prelaminate construction to asubstrate. Such process should avoid the problems of heated lamination,and should afford manufacturing flexibility. For example, such processshould permit the insertion or application of an additional layer orstructure after adhesive activation and before lamination to thesubstrate; and should allow the lamination of a variety of types offlexible substrates to the adhesively activated prelaminateconstruction.

SUMMARY OF THE INVENTION

There is provided in the practice of this invention, prelaminate PSAconstructions manufactured without second substrates, e.g., face stocks,that introduce manufacturing flexibility into the, process of makinglaminated PSA constructions. Prelaminate PSA constructions of thisinvention are nonblocking, thereby eliminating the possibility ofadhesive interference occurring between the prelaminate PSA constructionand a contiguous surface. Prelaminate PSA constructions of thisinvention are activatable in less than about five seconds to permitsubsequent lamination to a second substrate at a temperature less thanabout 100° C., i.e., a temperature significantly below a heat activationtemperature.

Prelaminate PSA constructions of this invention comprise, a firstsubstrate having a layer releasable material disposed thereon, a PSAlayer disposed on the layer of releasable material, and a detackifiedlayer (DL) disposed on a surface of the PSA layer. The DL can be formedfrom, in first and second construction embodiments, a detackifyingmaterial that is activatable to form a tacky layer on top of the PSAlayer; and in a third construction embodiment, from a detackifyingmaterial that is activatable to migrate into the PSA layer and revealthe PSA layer tacky surface. Preferred first and third embodimentdetackifying materials are heat activatable, while preferred secondembodiment detackifying materials are chemically activatable. In eachinstance the tacky surface is provided to accommodate subsequentlamination to a second substrate for forming a laminated PSAconstruction.

Prelaminate PSA constructions of this invention are completelynonblocking to a minimum 24 hour blocking temperature of at least 50° C.at a pressure of about 40 kilopascals (kPa). The nonblockingcharacteristics of the prelaminate PSA construction permits laminationto occur either: (1) after the step of manufacturing the prelaminate PSAconstruction during the same process operation; (2) after the step ofmanufacturing the prelaminate PSA construction during a separate processoperation at the same geographic location; or (3) after the step ofmanufacturing the prelaminate PSA construction during a separate processoperation at a different geographic location.

Laminated PSA constructions of this invention, prepared from first andsecond embodiment prelaminate PSA constructions, comprise a firstflexible substrate having a layer of releasable material disposedthereon, a layer of PSA disposed on the layer of releasable material, aDL disposed on a surface of the PSA layer, and a second substratelaminated to a surface of the DL. Laminated PSA constructions formedfrom first embodiment prelaminate PSA construction have improvedproperties of structural rigidity and shear when compared toconventional laminated PSA constructions that do not include the DL. Forthis reason, the DL in such embodiment is a reinforcing material.

Furthermore, the DL of the first and second embodiment prelaminate PSAconstructions acts as a barrier to prevent the migration oflow-molecular weight species from the pressure sensitive adhesive to thesecond substrate, which can stain the second substrate.

Laminated PSA constructions of this invention, prepared from a thirdembodiment prelaminate PSA construction, comprises a first flexiblesubstrate having a layer of low-release material disposed thereon, alayer of PSA disposed on the layer of low-release material that includesdetackifying material constituents disposed therein, and a secondsubstrate laminated to a surface of the PSA layer.

Prelaminate PSA constructions of this invention: (1) introduceflexibility into the process of manufacturing PSA construction byallowing the prelaminate PSA constructions to be stored, handled ortransported before lamination, thereby eliminating the need to laminateimmediately after PSA formation; (2) permit lamination at low or ambientprocess temperature conditions, thereby maximizing the type ofsubstrates that can be used with the construction and eliminatingproblems that are otherwise known to occur during heated lamination; and(3) enhance the physical properties of the laminated PSA construction.

DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome appreciated as the same becomes better understood with referenceto the specification, claims and drawings wherein:

FIG. 1 is a semi-schematic side elevation of a method of manufacturing aconventional PSA construction;

FIG. 2 is a semi-schematic side elevation of a method of applying a facestock to the PSA construction in FIG. 1 to form a laminated PSAconstruction;

FIG. 3 is a semi-schematic side elevation of a conventional method ofconverting the laminated PSA construction produced in FIG. 2;

FIG. 4 is a cross-sectional side elevation of a conventional PSA labelconstruction;

FIG. 5 is a cross-sectional side elevation of first, second and thirdembodiments of prelaminate PSA constructions prepared according toprinciples of this invention;

FIG. 6 is a top plan elevation of a prelaminate PSA subconstructioncomprising a release liner having a patterned layer of low-releasematerial;

FIG. 7 is a cross-sectional side elevation of first and secondembodiment prelaminate PSA constructions after activation;

FIG. 8 is a cross-sectional side elevation of a third embodimentprelaminate PSA construction after activation;

FIG. 9 is a semi-schematic side elevation of a first method ofmanufacturing prelaminate PSA constructions of this invention;

FIG. 10 is a semi-schematic side elevation of a second method ofmanufacturing prelaminate PSA constructions of this invention;

FIG. 11 is a semi-schematic side elevation of a method of activatingfirst and second embodiment prelaminate PSA constructions of thisinvention and applying a second substrate thereto;

FIG. 12 is a semi-schematic side elevation of an alternative method ofactivating first and second embodiment prelaminate PSA constructions ofthis invention and applying a second substrate thereto using preheating;

FIG. 13 is a cross-sectional side elevation of first, second and thirdembodiment prelaminate PSA constructions of this invention havingadhesive free zones;

FIG. 14 is a cross-sectional side elevation of first and secondembodiment laminated PSA constructions;

FIG. 15 is a cross-sectional side elevation of a third embodimentlaminated PSA construction; and

FIG. 16 is a semi-schematic side elevation of a method of heat treatingthe DL of prelaminate PSA constructions of this invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to prelaminate PSA constructions whichdo not include a second substrate, e.g., a face stock and the like, andwhich comprise a first flexible substrate, a coating of release materialdisposed on a surface of the flexible substrate, a pressure-sensitiveadhesive disposed on the coating of release material, and a DL depositedonto a surface of a pressure-sensitive adhesive layer. Prelaminate PSAconstructions of this invention are nonblocking, thereby facilitatingstorage, handling, and transportation of the construction, and providingflexibility in the process of manufacturing laminated PSA constructionstherefrom.

Prelaminate PSA constructions of this invention are designed tofacilitate subsequent lamination to a desired second substrate attemperature conditions significantly below that used for activation ofthe construction, e.g., at ambient to subactivation processtemperatures, without the need to heat the substrate or heat the nipduring lamination. The ability to laminate at such temperatureconditions maximizes the different types of substrates that can be usedwith prelaminate PSA constructions of this invention.

Prelaminate PSA constructions of this invention offer many advantagesover conventional PSA constructions, such as conventional PSA labelconstructions illustrated in FIG. 4. With reference thereto, aconventional PSA label construction 26 comprises a liner 28 havingdisposed thereon a coating of release material 30, forming a releaseliner. A PSA layer 32 is disposed on the coating of release material 26.A face stock 34, in sheet stock or roll stock form, is disposed on asurface of the PSA layer 32.

In a conventional PSA label construction, comprising the release liner28, coating of release material 30, and PSA layer 32, is manufacturedand laminated together with the face stock 34 during a single process,e.g., by a roll coating and lamination process or by a die coating andlamination process. The completed or laminated PSA label construction isdistributed to a converter where it is printed, cut and stripped, e.g.,by die cutting and matrix stripping methods as described above, to formthe desired shape and size label. It is to be understood that theconverting operation may proceed differently than that described above,depending on the particular PSA label application. For example, theconverting step may include the steps of cutting and stripping that isfollowed by the step of printing.

For purposes of increasing manufacturing flexibility, prelaminate PSAconstructions of this invention allow for a prelaminate PSA constructionto be manufactured independent of subsequent lamination with asubstrate, thereby permitting PSA construction lamination to occureither: (1) after the step of manufacturing the prelaminate PSAconstruction during the same process operation; (2) after the step ofmanufacturing the prelaminate PSA construction during a separate processoperation at the same geographic location; or (3) after the step ofmanufacturing the prelaminate PSA construction during a separate processoperation at a different geographic location.

With reference now to FIG. 5, an exemplary embodiment of a prelaminatePSA construction 36, prepared according to principles of this invention,includes a first substrate 38 and a coating of release material 40disposed on a surface of the first substrate 38. It is to be understoodthat the first substrate may be in the form of any material suitable toact as a carrier for the construction. Preferred first substratesinclude flexible materials that are selected from the group of stocksselected from sheet stock and roll or web stock. A particularlypreferred first substrate is a web stock in the form of a liner having arelease material disposed thereon, thereby forming a release liner. Aparticularly preferred release liner is one that is commerciallyavailable from, for example, Rhinelander Paper of Rhinelander, Wis.under the product name Rhi-Liner 12, that has a thickness of about 65micrometers and has a 42 pound basis weight.

Suitable release materials include those materials with a low surfacefree energy that have a low affinity for the PSA, thereby allowing thePSA to be peeled away without cohesive failure. Preferred releasematerials are selected from the group of silicone-containing materials.A particularly preferred silicone-containing material for forming thecoating of release material is commercially available from, for example,General Electric Silicones of Waterford, N.Y. under the product name GE6000.

A layer of PSA 42 is disposed on a coating of release material 40, and aDL 44 is disposed on a surface of the PSA layer 42. The PSA layer 42 hasa body portion and has a surface portion that is oriented immediatelyadjacent the DL 44. The DL 44 acts to detackify the underlying PSA layer42, thereby forming a nonblocking prelaminate PSA construction thatenables subsequent handling or treatment of the construction without itadhering to itself or to any other adjacent surface.

There are three prelaminate PSA constructions that are preparedaccording to principles of this invention. Each prelaminate PSAconstruction embodiment comprises an outermost DL that renders theconstruction completely nonblocking until it is activated to facilitatelamination. A first embodiment prelaminate PSA construction comprises aDL that is formed from a detackifying material that is capable of beingheat activated to form an activated tacky layer on top of the PSA layerto facilitate lamination. A second embodiment prelaminate PSAconstruction comprises a DL that is formed from a detackifying materialthat is capable of being chemically activated to form an activated tackylayer on top of the PSA layer to facilitate lamination. A thirdembodiment prelaminate PSA construction comprises a DL that is formedfrom a detackifying material that is capable of being heat activated tomigrate into the PSA layer to expose the underlaying tacky PSA surfaceto facilitate lamination.

The DL that is applied to the PSA layer is in the form of a continuousfilm that completely covers the underlying PSA layer, and renders theprelaminate PSA construction completely nonblocking. Prelaminate PSAconstructions of this invention are known to be nonblocking up to aminimum temperature of at least 50° C., and in some instances up toabout 70° C., for a 24 hour period under a pressure of about 40 kPa, aswill be discussed in greater detail below.

It is important that prelaminate PSA constructions of this inventiondisplay such nonblocking characteristics to facilitate removing orseparating the collected and/or stored prelaminate PSA construction fromcontiguous layers after it has been manufactured without causing therelease liner to be pulled free of the PSA layer. The use of the releasematerial on the release liner allows the release liner to be easilyremovable from the PSA layer to facilitate attachment of the completed,i.e., laminated, PSA construction to a desired article. Adhesiveinterference or blocking between the DL and an adjacent backside surfaceof the release liner is not desired because it results in the releaseliner being pulled away from the PSA layer during the removal orseparation operation, thereby rendering the prelaminate PSA constructionuseless.

If desired, the release liner may be patterned to avoid the possibilityof the PSA layer lifting away from the lengthwise edges of the formedand collected PSA construction, and thereby interfering with the payoutof the prelaminate PSA construction during the activation and laminationoperation by adhering to the adjacent backside surface of the releaseliner. Referring to FIG. 6, in an alternative embodiment of theprelaminate PSA construction 46, the release liner 48 is patterned sothat the coating of release material 50 is not deposited along eachlengthwise edge 52. The distance that each patterned portion extendsaway from a respective lengthwise edge and across the width of therelease liner depends on the particular application. In an exemplaryembodiment, a patterned portion extending up to about three millimetersfrom the lengthwise, i.e., machine direction, edge has proven adequate.

Additionally, in the event that the prelaminate PSA construction is tobe slit lengthwise after formation to form two or more different rolls,it may be desired that the release liner also be patterned along theslit point(s), as shown by 54, to prevent subsequent PSA layer liftingalong the newly-formed lengthwise edges.

It is desired that the DL be formed from detackifying materials that arecapable of being used with a variety of conventional PSAs, includingsilicone-based PSAs, rubber-based PSAs, and acrylic-based PSAs. PSAsuseful in forming prelaminate PSA constructions of this inventioninclude those that are conventionally used in forming PSA constructions,such as rubber-based, silicone-based, and acrylic-based PSAs. Preferredadhesives systems are described in detail in U.S. patent applicationSer. No. 07/755,585 filed Sep. 3, 1991, abandoned on Sep. 25, 1992, andincorporated herein by reference.

PSAs useful in forming prelaminate PSA constructions according toprinciples of this invention can include:

S-246—A hot melt rubber based PSA that is manufactured by the FassonDivision of Avery Dennison Corporation.

S-490—An acrylic emulsion PSA that is manufactured by the ChemicalsDivision of Avery Dennison Corporation.

Some adhesives often contain low-molecular weight species which areliquid at room temperature. With respect to forming third embodiments ofprelaminate PSA constructions of this invention, i.e., prelaminate PSAconstructions comprising a heat activatable detackifying material havingconstituents that migrate into the PSA layer, it is preferred to keepthese materials to a minimum concentration. Low-molecular weight speciesinclude residual monomers, liquid tackifiers, liquid plasticizers andthe like which tend to exude during storage and can pass through the DL44, bloom and stain an adjacent second substrate laminated thereto.Materials that bloom can also cause undesirable blocking and adverselyaffect release from first substrate 38.

For acrylic adhesives, residual monomers are frequently encountered,which can be especially problematic since they tend to have low odorthresholds and, in some cases, behave as irritants.

In rubber-based hot melt PSAs, usually in addition to solid tackifiers,liquid plasticizers and liquid tackifiers are used. Tackifiers increaseglass transition temperature and plasticizers reduce glass transitiontemperature. Both act to modify tack and wet out. It is desired thatadhesives useful in forming third embodiments of prelaminate PSAconstructions of this invention not have large amounts of these liquidplasticizers and tackifiers.

The layer of PSA material can be applied to the first substrate forexample in the form of a hot melt, an emulsion or aqueous dispersion, asa solvent solution, or as a film membrane. The method that is used toapply the PSA material depends on the physical form of the PSA, and caninclude spray, roll, and die application methods. In preferredembodiments, the PSA material is applied in the form of a hot melt,solution, or emulsion by die application method. As will be discussedbelow, multi-die application methods can be used to simultaneously applythe PSA material along with the DL.

The type of detackifying material that is selected to form the DL mayvary depending on the type of material that is used to form the PSAlayer, and/or the type of second substrate to be laminated. For example,for a third embodiment prelaminate PSA construction that is activated bymigration of detackifying material constituents into the PSA layer, itis desired that the selected detackifying material have a solubilityparameter that complements and is compatible with the solubilityparameter of the PSA material. Such compatibility between the PSA and DLis needed to facilitate migration of detackifying material constituentsinto the body of the PSA during activation, thereby exposing theunderlying tacky surface of the PSA.

In contrast, for first and second embodiment a prelaminate PSAconstructions comprising a DL that is activated to form a second tackylayer, it is desired that the detackifying material have a solubilityparameter that is inconsistent or incompatible with that of the PSA.Such incompatibility is needed to ensure that the detackifying materialdoes not migrate into the PSA during activation.

Different methods can be used to apply the DL to the surface of the PSAlayer, depending on the type of detackifying material that is selected.Generally speaking, the methods described above for applying differentforms of the PSA material can also be used to apply the same forms ofthe detackifying material. For example, detackifying materials in theform of aqueous dispersions can be applied by roll coating, spraycoating or Meyer rod process; detackifying materials in the form of asolution or emulsion can be applied by die, spray, or roll process; anddetackifying materials in the form of a hot melt can be applied by roll,spray or die process.

If desired, the application methodology used for the DL can beindependent of both the detackifying material chemistry and theparticular method employed to apply the PSA layer. However, for purposesof manufacturing efficiency, it may be desirable to use a detackifyingmaterial that is in the same form as the PSA material so that the sameapplication methodology can be used for each. For example, when the PSAis in the form of a hot melt or a solution that is applied by dieprocess, it may be desired that the detackifying material also be in theform of a hot melt or solution to facilitate its application by a dieprocess, e.g., by multi-die process.

It is desired that the detackifying material be capable of beingactivatable to ready the prelaminate PSA construction for subsequentlamination with a second substrate. As referred to throughout thisapplication, the term “activation” generally refers to the process ofpreparing the prelaminate PSA construction for lamination to the secondsubstrate by forming a tacky surface. As described in greater detailbelow, this process may involve transforming the DL itself into a secondtacky layer on top of the PSA layer, or may involve the migration ofdetackifying constituents from the DL to the PSA layer body to exposethe underlying PSA layer tacky surface.

Depending on the type of detackifying material that is selected,prelaminate PSA constructions prepared according to principles of thisinvention can be activated by exposing the DL to: (1) heat byconductive, convective or radiative heat transfer means; or to (2)chemicals, such as solvents and the like.

FIG. 7 illustrates an activated first and second embodiment prelaminatePSA construction 56, prepared according to principles of this invention,that includes a DL that is activatable to itself form a second tackylayer 58 on top of the PSA layer 42 surface. In these embodiments it isnot necessary that the materials selected to form the DL and PSA layereach have a complementary solubility parameter because it is notnecessary that detackifying material constituents migrate or pass intothe PSA body. It is, however, desirable that the detackifying materialhave a chemistry that is both capable of forming an independent adhesivesurface and is compatible with the PSA layer during the activationprocess to form a strong interface or bond thereto.

First embodiment prelaminate PSA constructions prepared according toprinciples of this invention include a DL that is formed from adetackifying material that is heat activatable, while second embodimentPSA constructions include a DL that is formed from a detackifyingmaterial that is chemically activatable, e.g., activatable through useof a solvent.

FIG. 8 illustrates an activated third embodiment of a prelaminate PSAconstruction 60, prepared according to principles of this invention,that included a DL that was activatable to cause constituents 62 of thedetackifying material to migrate into the body of the underlying PSAlayer 42 to expose the tacky surface of the PSA layer and, thereby readythe construction for subsequent lamination with a second substrate. Insuch embodiment, it is desired that the detackifying material be in theform of a heat activatable non-staining coating which does not display atendency to migrate with time into the body of the PSA layer 42 until itis raised to an elevated temperature which is sufficient to causepermanent migration into the body of the PSA.

Upon sufficient heating, the detackifying material of the thirdembodiment migrates into the body of the PSA, leaving little or noresidue at the surface of the PSA and, thereby allows the adhesive torecover all or a substantial portion of its inherent pressure-sensitiveadhesive properties to facilitate lamination with a second substrate.

As discussed above, suitable techniques for applying the DL onto thesurface of the PSA layer include roll, spray, Meyer rod, electrostatic,and die process depending on the particular form of the detackifyingmaterial as mentioned above. The application techniques generally fallinto the category of either being a multi-step coating process, e.g.,application of first the PSA layer and then the DL, or a single-stepprocess, e.g., application of the PSA and DL together. In the multi-stepprocess, the DL can be applied to the surface of the PSA layer, afterthe PSA has been applied to the coating of release material on therelease liner, in the form of a hot melt, aqueous dispersion, orsolution by roll, spray, electrostatic, or die process. In thesingle-step process, die technology is preferably used to apply the DLonto the PSA layer simultaneously with applying the PSA layer onto thecoating of release material, in the form of a solution, emulsion or hotmelt.

An exemplary method of applying the PSA layer and DL onto a firstsubstrate in the form of a web stock by a multi-step die or tandem dieprocess 64 is illustrated in FIG. 9, where the PSA layer 66 is appliedin the form of a solution, emulsion or a hot melt, and the DL 68 issubsequently applied to the PSA layer 66 as a solution, emulsion or ahot melt. This method is illustrative of one that can easily beimplemented using existing PSA coating equipment to permit subsequentapplication of the DL. The PSA layer 66 is applied to the coating ofrelease material on the release liner 70 by a PSA coating station 72,which contains a volume of PSA material 74. A DL coating station 76 isdisposed downstream from the PSA coating station 72 and comprises avolume of detackifying material 78 for depositing onto the PSA layer 66.

In the event that the PSA layer and DL are each applied in the form of ahot melt, it may be desirable that a cooling platen (not shown) or thelike be placed between the PSA coating station 72 and the DL coatingstation 76, to cool the PSA layer 66 to prevent migration of the applieddetackifying material therein. It may also be desirable to place acooling platen (not shown) or the like after the DL coating station 76to cool the DL 68 to ensure that it is tack free before the prelaminatePSA construction is wound on a collection roll 80.

In the event that both the PSA layer and DL are applied in the form of asolution or emulsion, it may be desirable to place an evaporator (notshown) or the like between the PSA coating station 72 and the DL coatingstation 76, to drive the solution out of the PSA layer to prevent bubbleformation after application of the detackifying material. It may also bedesirable to place an evaporator (not shown) or the like after the DLcoating station 76 to drive the evaporatable species out of the DL 68before the prelaminate PSA construction is wound on the collection roll80.

As a continuous roll of the release liner 70 is unwound or dispersedfrom a pay out roll 82, the PSA coating station 72 deposits apredetermined thickness of PSA material 74 onto the coating of releasematerial on the release liner 70, forming a PSA layer 66 thereon. The DLcoating station 76 deposits a predetermined thickness of thedetackifying material 78 onto the surface of the PSA layer 66, as theprelaminate PSA subconstruction travels in a continuous web through theDL coating station 76, forming a DL 68 thereon.

In an exemplary embodiment, the PSA layer 66 has a coat weight in therange of from about 5 to 125 grams/square meter (g/m.sup.2), or has athickness in the range of from about 5 to 125 micrometers assuming a PSAdensity of about one. It is desired that the DL 68 have a coat 15 weightin the range of from about 0.5 to 100 g/m.sup.2 (0.5 to 100 micrometersthickness assuming a density of about 1), where a preferred DL coatweight is in the range of from about 1 to 50 g/m.sup.2 (1 to 50micrometers thickness), and where a most preferred DL coat weight is inthe range of from about 1 to 20 g/m.sup.2 (1 to 20 micrometersthickness). It is to be understood that the coat weight and layerthickness of both the PSA and detackifying material may vary dependingon the particular prelaminate PSA construction application. A DL havinga coat weight and/or thickness in the desired range provides a desireddegree of protection against adhesion between the PSA layer and anadjacent backside surface of a release liner when in the storedposition, and can be easily and efficiently processed during activationto either migrate into the underlying PSA layer or itself form a secondtacky layer to provide a desired degree of adhesion for supporting asecond substrate. If desired, the coat weight and/or thickness of eitherthe DL or PSA layer can be metered by use of a Meyer rod that can beplaced after each respective coating station.

To ensure accurate monitoring of the thickness of the DL, ultraviolet(UV) chromophores can be added to the detackifying material to allowvisual observation of coating quality during the application process,and to allow monitoring of the coat weight by on-line use of acombination ultraviolet and radio frequency gauge. A particularlypreferred UV chromophore is Leucopure EGM available from ClariantChemicals.

After the prelaminate PSA construction has passed the DL coating station72 and the detackifying material 78 has been applied, the prelaminatePSA construction is routed to and is collected on the collection roll80. When a desired quantity of the prelaminate PSA construction has beenmanufactured, the collection roll 80 is removed from the process and canbe stored for activation and lamination during a separate operation ateither the same or at a different geographic location, thereby providingenhanced manufacturing flexibility. Alternatively, rather than beingcollected, the completed prelaminate PSA construction can be routed foractivation and lamination during the same manufacturing operation.

An exemplary method of applying the PSA layer and DL by a single-stepmulti-die process 84 is illustrated in FIG. 10. A dual die station 86,comprising a PSA die chamber 88 and a DL die chamber 90, comprises aquantity of PSA material 92 and detackifying material 94 in respectiveseparated compartments. The dual die station 86 is used to deposit boththe PSA material and the detackifying material, in the form of either ahot melt, solution or emulsion, simultaneously in one step.

Although FIG. 10 illustrates a single-step multi-die process comprisinga dual die station for applying the PSA layer and DL, it is to beunderstood that the multi-die process may comprise a die station havingmore than two die compartments, depending on the number of layers to bedeposited onto the release liner. Multi-die application methods usefulfor applying both the PSA layer and the DL are further described inPublished PCT International Application Nos. PCT/US95/11807;PCT/US95/11733; PCT/US95/11734; and PCT/US95/11717, which are hereinincorporated by reference.

As a continuous roll of the release liner 96 is unwound from a pay outroll 98, the PSA die chamber 88 deposits a thickness of the PSA material92 onto the coating of release material on the release liner 96, forminga PSA layer 100 thereon. At the same time that the PSA material is beingdeposited, a thickness of the detackifying material 94 is deposited bythe DL die chamber 90 onto the just-formed surface of the PSA layer 100,forming a DL 102 thereon. The completed prelaminate PSA construction iscollected on a collection roll 104.

As discussed above, subsequent activation and lamination of theprelaminate PSA construction may occur at the same geographical locationwhere the prelaminate PSA construction was manufactured, or may occur ata different geographical location. Alternatively, rather than beingcollected, the completed prelaminate PSA construction can be routed foractivation and lamination during the same manufacturing operation.

In the event that the PSA layer and DL are applied as a hot melt, acooling platen (not shown) or the like can be placed between the dualdie station 86 and the collection roll 104 to reduce the temperature ofthe DL 102 to ensure that is tack free before being collected on thecollection roll 104, thereby avoiding unwanted sticking to the adjacentbackside surface of the release liner.

In the event that the PSA layer and DL are applied as a solution oremulsion, an evaporator (not shown) or the like can be placed betweenthe dual die station 86 and the collection roll 104 to drive off theevaporatable species from the prelaminate PSA construction before beingcollected on the collection roll 104 to avoid unwanted sticking to theadjacent backside surface of the release liner.

After the prelaminate PSA construction has passed the DL coating station72 and the detackifying material 78 has been applied thereto, it may bedesirable to further heat the DL to ensure that any streaks, surfaceimperfections or other voids that may have been formed therein and thatexpose the underlaying PSA layer are removed so that the DL is in theform of a continuous film before being collected. Such further heattreating step is helpful when the DL has a high solids content eitherduring or after its application. A DL applied as a hot melt, by eithermulti-step or tandem die process, has a solids content of approximately100 percent. Streaks or other surface imperfections that expose theunderlaying PSA layer may be formed in the DL during its application byparticulate matter in the die. Because of its high solids content, thedetackifying material is unable to readily migrate or flow after it isapplied to fill in such streaks or imperfections in the DL. If leftuntreated, the exposed PSA layer will be allowed to make contact with abackside surface of the release liner when the prelaminate PSAconstruction is collected on the collection roll.

Contact between the PSA layer and the contiguous release layer backsidesurface will cause the prelaminate PSA construction to adhere to suchbackside surface, thereby making the prelaminate PSA constructiondifficult to unwind and causing the PSA layer to bond permanently to therelease layer backside surface. Once the PSA layer is pulled away fromits underlaying release layer and is transferred to the backside surfaceof the contiguous release layer the PSA prelaminate construction isruined and is unsuited for lamination.

A DL that is applied as a solution or as an emulsion, by eithermulti-step or tandem die process, will have a solids content ofapproximately 100 percent after the solvent or emulsifying agent hasbeen evaporated away. Like the hot melt applied DL, the die process thatis used to apply a solvent or emulsion DL may also create streaks orother imperfections in the DL that exposes the underlaying PSA layer.Streaks or imperfections in the DL may be formed in solution or emulsionapplied DLs when either the DL does not adequately wet the underlyingPSA layer, or when the DL becomes dewetted with the underlaying PSAlayer during further processing, e.g., during evaporation. If leftuntreated, the streaks or imperfections could cause a catastrophicfailure of the prelaminate PSA construction as discussed above duringthe unwinding process by PSA layer transferal.

Streaking or the formation of other imperfections in the DL, that exposethe underlaying PSA layer, are eliminated by heat treating theprelaminate PSA construction at a stage after application of the DL butbefore the prelaminate PSA construction 212 is collected on a collectionroll 214. Heat treating the DL at this point causes the DL to soften,reflow and migrate to fill in any streaks or imperfections. Referring toFIG. 16, where the DL 102 is applied as a hot melt it is heat treated byexposure to a radiation, convention or conduction heating means asindicated generally by arrow 210 to a flow temperature that is below thedetackifying material activation temperature but sufficiently high tocause the detackifying material to reflow and fill any streaks orimperfections. In an example embodiment, where the DL is formed from thefirst embodiment detackifying materials discussed below and exemplifiedin Examples 1 and 2, the DL is heated to a temperature of approximately149° C. (300° F.) to cause it to flow a sufficient amount to fill allstreaks or imperfections that expose the underlying PSA, and therebyproduce a DL in the form of a continuous film the completely covers theunderlaying PSA layer.

Referring still to FIG. 16, where the DL 102 is applied in the form of asolvent or emulsion, the DL is heat treated by exposure to radiation,convention or conduction heating as indicated by arrow 210. Heattreating 210 the DL 102 can take place independently from theevaporation operation, and can be effecting by a heating means that isindependent of that used for the evaporating operation. Alternatively,the step of heat treating the DL 102 can be carried out as part of theevaporation operation by further heating the DL after evaporation to aflow temperature that is below the detackifying material activationtemperature but sufficiently high to cause the detackifying material toflow and fill any streaks or imperfections. In an example embodiment,where the DL is formed from the first embodiment detackifying materialsdiscussed below and exemplified in Examples 1 and 2, the DL is heated toa temperature of approximately 149° C. (300° F.) after being evaporatedto cause it to flow a sufficient amount to fill all streaks orimperfections that expose the underlying PSA, and thereby produce a DLin the form of a continuous film the completely covers the underlayingPSA layer.

In a preferred embodiment, where streaks or other imperfections arediscovered to be present in the DL, the DL is heat treated in threecontinuous zones using forced air convection ovens. The first zone washeated to 100° C., the second to 120° C., and the third to 140° C. Eachoven was approximately eight feet in length. The coated laminatetraveled at a speed of approximately 50 feet per minute, giving aresidence time of approximately 9.6 seconds through each zone.

Samples of prelaminate PSA constructions prepared according to theconditions discussed below were tested to determine the surfaceroughness of the DL before and after being heat treated in the mannerdiscussed immediately above. The DL of a non-heat treated prelaminatePSA construction had an average surface roughness of approximately 0.87micrometers, and a RMS surface roughness of approximately 1.08, whenmeasured using a Wyco surface morphology microscope scanned at amagnification of approximately 5.3 times, using a scan area ofapproximately 1170.times.880 micrometers, and using a point-to-pointdistance of approximately 3.10 micrometers. The DL of a heat treatedprelaminate P SA construction had an average surface roughness ofapproximately 0.58 micrometers, and a RMS surface roughness ofapproximately 0.71 micrometers under the same measurement conditions.Based on these results, the process of heat treating the DL as describedherein reduced the surface roughness of the DL by approximately 40percent, thereby evidencing the filling and minimization of streaks andother imperfections in the DL. Additionally, the heat treated DL alsodisplayed a surface finish that was glossier than that of the non-heattreated prelaminate PSA construction.

A feature of prelaminate PSA constructions of this invention is thatthey promote flexibility in the manufacturing process by providing acompletely nonblocking prelaminate PSA construction that is capable ofbeing activated and laminated at a later time and/or at a differentgeographic location independent of where the construction wasmanufactured.

While particular methods for manufacturing prelaminate PSA constructionshave been described and illustrated, it is to be understood thatconventional methods for applying PSA materials, and for making PSAconstructions, can also be adapted to manufacture prelaminate PSAconstructions of this invention.

Suitable detackifying materials useful for forming first embodiments ofprelaminate PSA constructions, that are capable of being heat activatedto transform the DL into a second tacky layer (as shown in FIG. 7),include heat-seal adhesives, modified heat-seal adhesives, anddelayed-action heat-seal adhesives that: (1) are good continuous filmformers; (2), are capable of completely and uniformly covering theunderlying PSA layer; and (3) have inherent properties of open tack.Exemplary detackifying materials are thermoplastic heat-seal adhesivesselected from the group including polyamide resins, polyester resins,polyurethane resins, polyacrylate resins, ethylenevinylacetate resins,and mixtures thereof.

It is desired that the detackifying material selected to form first andsecond embodiment prelaminate PSA constructions produce a second tackylayer that has a higher degree of adhesion to a laminated secondsubstrate than the degree of adhesion between the PSA layer and therelease liner to facilitate preferable release of the release liner fromthe laminated construction to ready the laminated PSA construction forapplication onto a desired object.

When the detackifying material used to form the first embodimentprelaminate PSA construction is applied in the form of a hot melt,solution, or emulsion by dual die method, it is desired that thedetackifying material have a hot melt, solution, or emulsion viscosityduring the coating operation that is within a viscosity window similarto that of the PSA material. This is desired to enable the detackifyingmaterial to form a continuous film that completely and uniformly coversthe underlying PSA layer, thereby forming a nonblocking prelaminate PSAconstruction. The simultaneous delivery of the PSA and detackifyingmaterial is possible using conventional coating equipment and amulti-die or an extruder if the viscosities between the respectivematerials are relatively close and the two materials do notsignificantly interact with each other. When applied simultaneouslyusing conventional die methods it is desired that the PSA anddetackifying material have a hot melt viscosity and melting temperaturethat are relatively similar. The use of polyamide resins in particularare suitable detackifying materials for conventional hot melt adhesivesbecause their viscosities are similar in magnitude at the applicationtemperatures used to deliver the respective materials.

For example, when the PSA is a conventional hot melt adhesive, themelting temperatures of the PSA are in the range of from about 150° C.to about 200° C., and preferably in the range of from about 165° C. toabout 180° C. It is, therefore, desired that the detackifying materialselected for use with such PSA have a melt temperature below about 200°C., and preferably in the range of from about 150° C. to 180° C.

Conventional hot melt PSAs have a Brookfield viscosity in the range offrom about 25,000 to 90,000 centipoise at 175° C. It is desirable thatthe detackifying material that is used with such PSA have a viscositythat is within a factor of about two times that of the PSA. Adetackifying material having a hot melt, solution, or emulsion viscositymore than about a factor of two times below that of the PSA material canproduce a DL having film defects that prevent complete and uniform PSAlayer coverage. A detackifying material having a hot melt, solution, oremulsion viscosity having a factor of about two times greater than thePSA material can produce a DL that also displays film defects, therebypreventing complete and uniform PSA layer coverage. Preferreddetackifying materials have a hot melt, solution, or emulsion viscositywindow during coating by dual die process within a factor of about twopercent that of the viscosity of the just-applied PSA material.

It is desired that the detackifying material, selected to form first andsecond embodiment prelaminate PSA constructions also have a chemistrythat is not compatible with the underlying PSA material to prevent itsmigration into the PSA layer during activation. Migration of thedetackifying material into the PSA layer is not desired in suchembodiment of the prelaminate PSA construction because it can reduce theadhesion performance of the functional PSA underlayer.

A key desired feature of the detackifying material used to form thefirst embodiment prelaminate PSA constructions is that it have an opentack time that both facilitates prelaminate PSA constructionmanufacturing efficiency, and permits lamination at ambient orsubactivation process temperature conditions. “Open tack” refers to theamount of time that a just-deposited or just-activated detackifyingmaterial remains tacky or open to adhesive contact with an adjacentsurface. Certain polymers, when heated to their melting temperature andcooled, require an amount of time to fully harden. During such time thepolymer can remain tacky. This period after cooling where the polymerremains tacky permits ambient or subactivation temperature lamination ofa second substrate to the tacky surface, which is highly desirable.

During the process of manufacturing the prelaminate PSA construction itis desired that the open tack time be as short as possible to facilitatecollecting the prelaminate PSA construction shortly after thedetackifying material is applied, thus speeding up the rate ofmanufacture. However, it is also desired that the open tack time besufficiently long to allow the just-activated detackifying material timeto cool before lamination, thereby permitting ambient processtemperature or subactivation lamination. Open tack, therefore,represents a compromise between competing process concerns.

In an exemplary embodiment, it is desired that the detackifying materialhave an open tack time greater than about 0.25 seconds and less thanabout twenty seconds, and preferably less than about five seconds afteractivation. To reduce the open tack time during the process oflaminating the prelaminate PSA construction, and thereby speed up therate at which the construction is laminated, the just-activatedprelaminate PSA construction may be cooled before lamination by use of aconventional cooling means placed between the activation means and thelamination means. Cooling the just-activated prelaminate PSAconstruction allows lamination to occur at ambient or subactivationprocess temperature conditions shortly after heat activation.

It is also desired that detackifying materials selected to form first,second and third embodiment prelaminate PSA constructions of thisinvention be capable of being activated in a relatively short period oftime to facilitate activation and lamination efficiency. Preferreddetackifying materials useful in forming DLs of this invention arecapable of being activated in less than about five seconds, and morepreferably in about one second. For first and third prelaminate PSAconstruction embodiments, such activation is achieved by exposing the DLto heat at a predetermined temperature for a period of less than aboutfive seconds, and for second embodiment prelaminate PSA constructionssuch activation is achieved by exposing the DL to a suitable chemicalfor a period of less than about five seconds.

It is also desired that the detackifying material, selected to formfirst and second embodiment prelaminate PSA constructions, act as abarrier to prevent the migration of unwanted PSA constituents to thelaminated second substrate and visa versa. The migration of such PSAconstituents, such as mobile oils and tackifying resins and the likeused in hot melt PSAs, to the second substrate is not desired because itcan degrade and damage the cosmetic and functional features of thelaminate. Additionally, migration of constituents from the secondsubstrate into the PSA layer may adversely affect the adhesiveperformance of the PSA. The barrier function of the detackifyingmaterial is also desired because it allows for the use of porous secondsubstrates that otherwise would not hold up because of the migration ofsuch constituents.

Preferred heat-seal adhesives are thermoplastic polyamide resins.Particularly preferred polyamide resins are those commerciallyavailable, for example, from Union Camp of Wayne, N.J. under the Uni-Rezproduct line. Polyamide resins available from General Mills, Inc., ofMinneapolis, Minn. under the Versamid product name can also be used.Other suitable polyamides include those produced by condensing dimerizedvegetable acids with hexamethylenediamine.

Referring to the Union Camp heat-seal adhesives, the particular Uni-Rezpolyamide resin or resin blend that is selected ultimately depends onthe particular prelaminate PSA construction application and, morespecifically, depends on the viscosity of the PSA material used to formthe underlying PSA layer. In an exemplary embodiment, where theunderlying PSA material is S-246, a preferred polyamide resin comprisesa blend of Uni-Rez resins that provides a desired viscosity within therange described above. In an exemplary embodiment, where the underlyingPSA material is S-246, a preferred detackifying material formed from thepolyamide resin comprises a blend of Uni-Rez resins that provides adesired viscosity within the range described above. For example, a 1:3mixture of the Uni-Rez 2620 and 2623 polyamide resins produces a blendhaving a Goettfert viscosity curve at 155° C., within a shear rate rangeof from 0 to 40,000 seconds.sup.-1, that is within a factor of about twotimes the Goettfert viscosity curve at 155° C. for the S-246 PSAmaterial.

Table 1 below sets forth example Uni-Rez polyamide resins useful asdetackifying materials in this invention, either alone or incombination. Additionally, as noted in Table 1 below, polyamide resinsuseful as detackfying materials for this invention form inherentlyself-supporting films that exhibit properties of tensile strength and,elongation. As will be better discussed below such supporting propertiesare desired for the reinforcing effect that such materials provide tothe laminated PSA construction, which can be beneficial for convertingand dispensing operations.

1TABLE 1 Softening Viscosity Tensile Uni-Rez Point (cPs at StrengthPercent product code (° C.) 190° C.) (Psi) Elongation Peel 2620 105 9001,000 50 0 2623 136 6,500 1,000 400 0 2665 165 11,000 2,000 500 0 2695128 5,000 200 175 30 2620 & 2623 128 5,100 1,000 313 0 (1:3 blend)

Preferred modified heat-seal adhesives include those heat-seal adhesivespreviously described that additionally include one or more plasticizersand/or tackifiers to make them behave more like PSAs during their opentack time period. An exemplary modified heat-seal adhesive is apolyamide resin formed by condensing equal molar amounts of Hystrene3695 dimer acid available from Humco of Texarkana, Tex. withhexamethylenediamine, taking 50 percent by weight of such polyamideresin and adding to it about 25 percent by weight castor bean oil, and25 percent by weight Foral 85 rosin ester tackifier from Hercules Inc.,of Wilmington, Del.

Delayed-action heat-seal adhesives useful for forming first embodimentprelaminate PSA constructions of this invention are formed from polymersthat normally do not possess open tack, but are mixed with one or moresolid plasticizer. When melted, the solid plasticizer causes thenontacky polymer to become tacky, and remains liquid for some time aftercooling to provide an open tack. Suitable delayed-action heat-sealadhesives are commercially available from, for example, Kimberly-Clark,Brown Bridge Industries of Troy, Ohio under the product names 402-MC,64-BAK, 441-BL and 70-RECA; Oliver Products Company of Grand Rapids,Mich. under its Engineered Adhesive Coated Products line; and NashuaGraphic Products of Merrimack, N.H. under the product names RX-1, BM-4,PBL-3, as described in U.S. Pat. Nos. 2,462,029, 3,104,979, and2,678,284, which are each herein incorporated by reference.

The heat seal adhesives, particularly the polyamides, serve yet anotherimportant function in the post-utilization of the label and tapeconstructions of this invention. It has been found that when the facestock or backing is paper, and when paper is destined to be recovered ina pulping operation, that the heat seal adhesive can be used to retainthe pressure-sensitive adhesive substantially intact during the pulpingoperation, such that the repulped paper fibers will pass through ascreen while the detack layer serves to prevent the polymers forming thepressure sensitive adhesive from contaminating the repulped paperfibers. This finding is particularly useful in the treatment of wastepapers containing label and tape products where processing is normallyexpected to result in the formation of “stickies”. It enables removal ofa contaminate from paper pulp early in the fiber recovery and thedeinking processes.

The paper industry have become favorable towards a screenable adhesiveapproach to paper fiber recovery processes which has been in use bynon-pressure sensitive adhesive manufacturers. The limitation of thisapproach for a pressure-sensitive adhesive is that pressure sensitiveadhesives are engineered to be elastic and deformable and will readilypass through even fine screens. The use of a laminate constructionaccording to this invention enables one to take advantage of therelatively non-elastic film forming characteristics of the polyamide DLto separate the pressure sensitive adhesive from paper pulp, as thepolyamide layer will not fragment into smaller particles and willaggressively retain the adhesive to itself during the paper defiberingprocess. Further, the use of polyamides is desired in such applicationbecause they are known to form a bond with the PSA layer that isstronger than one formed with the face stock, thereby providing thepreferential release of the face stock and the preferential binding ofthe PSA during the pulping operation.

Consequently, the pressure sensitive adhesive can be readily removed,intact and on relatively non-flexible and three dimensional carrier. Thelabel face stock paper and substrate paper will completely pulp from theadhesive-polyamide film layer with the adhesive firmly attached to thepolyamide layer. For use in such application, the polyamide DL layer ispreferably applied at a weight of about 4 to about 15 g/m.sup.2 anddeposited as a hot melt, solvent or emulsion layer. Although the use ofpolyamides have been discussed for purposes of forming a repulpablelaminated PSA construction, other compounds that satisfy therequirements of the detackifying material discussed above, and that areadditionally capable of forming: (1) a substantially non-elastic filmlayer; and (2) a relatively stronger bond with the PSA layer than withthe face stock to preferentially tie up or bind up the PSA, can also beused to form repulpable laminated PSA constructions of this invention.

Detackifying materials used for forming first embodiment prelaminate PSAconstructions of this invention are preferably applied by single-stepmulti-die process as previously described and illustrated in FIG. 10,and are preferably applied as a hot melt.

FIG. 11 illustrates an exemplary activation/lamination station 106 thatis used to activate and laminate first embodiment prelaminate PSAconstructions of this invention embodied in web stock form. Theactivation/lamination station 106 comprises a pay out roll 108 thatunwinds or disperses a continuous roll of the prelaminate PSAconstruction 110 over a first roller 112 and over an activating means114, where DL is heated to a temperature in the range of from about 100to about 150° C. It is to be understood that the prelaminate PSAconstruction 110 illustrated in FIG. 11 comprises a multi-layerconstruction made up of a release liner, i.e., a liner having a coatingof release material disposed thereon, a PSA layer disposed on a surfaceof the release liner, and a DL disposed on the PSA layer, but has beensimplified for purposes of illustration by showing only a singlethickness.

The activating means 114 may be selected from those devices that areconventionally used for heating processes and that are capable oftransferring heat to the DL by conductive, convective or radiant heattransfer means. In an exemplary embodiment, the activating means 114 isin the form of a heated platen operated at a temperature in the range offrom about 75 to about 175° C., that relies on conductive heat transferto heat the DL. The activation operation is controlled so that a portionof the prelaminate PSA construction has contact with the activatingmeans for up to about five seconds, and preferably about one second.

The just-activated prelaminate PSA construction is routed to laminatingmeans 116 in the form of rollers 118, where the just-activatedprelaminate PSA construction 110 is forced into contact with a secondsubstrate 120 and laminated thereto. In an exemplary embodiment, therollers are adapted to impose a pressure of about ten Newtons/millimeterupon the prelaminate PSA construction and second substrate.

The second substrate useful for forming laminated PSA constructionsaccording to principles of this invention can be formed from any type offlexible material suitable for use with a PSA construction. For example,the second substrate can be in the form of a sheet stock that isutilized in separate sheet form, or roll or web stock that is utilizedin a continuous roll. Face stock which is formed into labels is usuallywound and unwound in web form and is one form of a web stock that can belaminated to prelaminate PSA constructions of this invention. Examplesof second substrate useful for laminating first, second and thirdactivated prelaminate PSA constructions of this invention include butare not limited to labels, label stock, decorative web or sheet stock,signage material and the like that may be formed from paper, foilpolymeric film, cardstock, foam, fabric or cloth and the like. Thesecond substrate can be a single layer material, or alternatively mayconsist of a multi-layer construction.

In one embodiment of a multi-layer second substrate, the secondsubstrate may comprise another prelaminate PSA construction of thisinvention. Accordingly, first, second and third prelaminate PSAconstructions of this invention can be activated and laminated toanother activated or unactivated first, second and third prelaminate PSAconstruction to form a laminated construction having dual firstsubstrates or release liners. Such laminated constructions can be formedby using the same prelaminate constructions, e.g., by laminating a firstembodiment prelaminate PSA construction to a first embodimentprelaminate PSA construction, or can be formed by using differentprelaminate constructions, e.g., by laminating a first embodimentprelaminate PSA construction to a second embodiment prelaminate PSAconstruction.

Laminated PSA constructions comprising a second substrate formed fromanother prelaminate PSA construction may used in applications where itwould be advantageous to have PSAs, each having different adhesiveproperties, at the first and second substrate interface. The use of PSAshaving different adhesive properties at each substrate interface may bedesirable in applications where the first and second substrates beingused are of a different type. For example, a hot melt PSA may be used atan interface with a substrate having a low surface energy surfacebecause of the desired adhesion between hot melt PSAs and low surfaceenergy surfaces, while a emulsion PSA may be used at an interface with asubstrate having a corrugated surface because of the desired adhesionbetween emulsion PSAs and corrugated surfaces.

Laminated PSA constructions comprising a second substrate formed fromanother prelaminate PSA construction may also be used as a transfertape, where each substrate is in the form of a release liner that isremovable from each respective PSA to facilitate adhering the PSAconstructions between two objects after removing both release liners.

Although in FIG. 11 the second substrate 120 is shown to be in the formof a web stock that is unwound from a roll 122, it is to be understoodthat a second substrate in the form of sheet stock can be used to thesame degree. Such sheet stock may, for example, consist of a series ofarticles bonded to the activated prelaminated construction in a spacedapart arrangement. In this embodiment (not shown in the drawings), thesecond substrate is not coextensive with the prelaminate construction,so that a portion of the activated adhesive surface remains exposedafter the lamination step. Using the DL of the first embodiment, theexposed portion of the DL loses its tack shortly after lamination.

As the first embodiment prelaminate PSA construction passes over theactivating means 114 and is heated, the DL undergoes physical change andis transformed into a second tacky layer. The second tacky layer has asufficient open tack time to permit subsequent lamination without havingto heat the second substrate 120, thereby allowing the second substrateto be laminated thereto under ambient or subactivation processtemperature conditions, i.e., without having to apply further heat atthe nip or to the second substrate. The completed PSA construction 124,comprising a second substrate 120, is collected on a collection roll 126for storage or for subsequent conversion, e.g., printing, die cuttingand matrix stripping as discussed above.

In use, the second substrate 120 remains permanently joined to thepreviously activated tacky layer of the prelaminate PSA construction110, and the PSA is separated from the release liner to permit adhesionof the second substrate to a desired object or article.

The ability to provide a prelaminate PSA construction that is heatactivatable to permit ambient or subactivation process temperaturelamination, i.e., lamination at temperature conditions well belowactivation temperature, is a key feature of prelaminate PSAconstructions of this invention for several reasons. Avoiding the needto heat the second substrate maximizes the different types of substratematerials than can be used with the prelaminate PSA construction,thereby further maximizing manufacturing flexibility. For example, theprocess of ambient or subactivation process temperature laminationallows the prelaminate PSA construction to be used with a wide varietyof face stock paper such as thermal print paper, paper and polymericfilms having a low glass transition temperature and the like, thatotherwise cannot be used in applications calling for heated lamination.

The process of ambient or subactivation process temperature laminationalso avoids problems that are otherwise known to occur at the nip underconditions of heated lamination, such as wrinkling and buckling and thelike, that are caused by different coefficients of expansion between theprelaminate PSA construction and the second substrate. Additionally, theprocess of ambient to subactivation process temperature laminationavoids face stock shrinkage that is known to occur in paper face stocksdue to the loss of water that occurs during heated lamination, which cancause curling and the like. Ambient or subactivation process temperaturelamination also avoids outgassing of steam or other vapors in the nipthat is known to occur during heated lamination, which causes bubbleformation at the nip and produces areas of poor anchorage.

Although a key feature of prelaminate PSA constructions of thisinvention is the ability to laminate after activation without having tofurther heat the activated prelaminate PSA construction or secondsubstrate, in some situations it may be desirable to introduce furtherheat to the activated prelaminate PSA construction or to the secondsubstrate, e.g., at the nip and the like, to achieve a desiredequilibrium nip temperature that is higher than the otherwise ambientnip temperature. Additionally, in some situations it may be desired tocool the activated prelaminate PSA construction or second substrate toachieve an equilibrium nip temperature that is lower than the otherwiseambient nip temperature.

As used herein, the term “equilibrium nip temperature” is understood torefer to the temperature that is achieved at the nip under steady stateconditions. The term “ambient temperature” or “ambient processtemperature” is understood to refer to the temperature that is achievedat the nip under steady state conditions without further heating orcooling the activated prelaminate PSA construction before lamination.

Equilibrium nip temperature is achieved by the cooling of the activatedprelaminate PSA construction that occurs by contact that is made withthe relatively cooler rollers and second substrate. Variations in theprelaminate PSA construction and the second substrate can affect theheat transfer capability of the construction and can, therefore,influence the equilibrium nip temperature. Because of such variations,it may be desired to further heat or cool the activated construction orsecond substrate to achieve a desired equilibrium nip temperature.

It is to be understood, however, that in all circumstances theequilibrium nip temperature is significantly less than the activationtemperature. In a preferred embodiment, the equilibrium nip temperatureis between the activation temperature and the ambient temperature, andmore preferably is less than about 100° C. In an exemplary embodiment,referring to first and third embodiment prelaminate PSA constructionscomprising heat activatable detackifying materials, the equilibrium niptemperature without added heating or cooling at the nip is at an ambientprocess temperature of about 70° C.

With reference to the second embodiment prelaminate PSA construction,comprising a chemically-activatable detackifying material, it is to beunderstood that the equilibrium nip temperature without added heating orcooling is at an ambient process temperature near or at ambient roomtemperature.

For example, it may be desired to add further heat to the nip to raisethe equilibrium nip temperature to a desired temperature above theotherwise ambient temperature in circumstances where a reduced pressurelamination is desired. It may be desired to cool the nip to reduce theequilibrium nip temperature to a desired temperature below the otherwiseambient temperature in circumstances where the mass of the activatedprelaminate PSA construction is large and/or the mass of the secondsubstrate is small.

Examples illustrative of first embodiment prelaminate P SAconstructions, comprising heat activatable detackifying materialscapable of forming a second tacky layer, are as follows:

EXAMPLE 1 First Embodiment Prelaminate PSA Construction

A first embodiment prelaminate PSA construction was prepared by hot meltdual die method by applying a PSA layer comprising S-246 adhesive to a42 pound basis weight Rhi-Liner 12 release liner comprising a layer ofGeneral Electric 6000 silicone release material. A DL comprising a blendof Uni-Rez 2620 and 2623 polyamide resin was simultaneously applied to asurface of the PSA layer. The coat weight of the PSA adhesive was about20 g/m.sup.2, or about 20 micrometers thick. Five grams of Leucopure EGMUV chromophore was added to about five gallons of the polyamide blend ata blend ratio of one gram Leucopure per gallon resin to permit visualobservation of the DL under a UV light. The polyamide resin blendcomprised about 25 percent by weight 2620 and 75 percent by weight 2623.The polyamide resin was applied at a coat weight of about 10 g/m.sup.2,or about 10 micrometers thick. The resulting DL had an open time of lessthan about five seconds.

The prelaminate PSA construction was heat activated by running thebackside surface of the release liner over a heated platen that was setfor about 175° C. The speed of the web unwinding was set to provide aprelaminate PSA construction exposure time to the heated platen of aboutone second. The ambient process temperature at the lamination nip wasestimated to be about 70° C. The lamination was carried out at a speedof about 40 feet/minute, and the nip was positioned about six inchespast the trailing edge of the heated platen.

The activated prelaminate PSA construction was laminated to a number ofdifferent face stock materials, including thermal print paper and 50pound uncoated litho paper. In all cases, anchorage was excellent andthere was no thermal damage to the face stock.

Lay flat tests were conducted on 216 millimeter by 280 millimeterrectangular-shaped samples of the above-prepared laminated PSAconstruction comprising the 50 pound uncoated litho paper. Lay flattests were also conducted on conventional PSA constructions comprising a50 pound clay coated machine finish paper release liner, an acrylicemulsion PSA disposed thereon, and a 50 pound uncoated wood-freehigh-quality laser face stock.

During the tests, the samples were placed in a constant humidity chamberoperated at 25, 50 and 75 percent relative humidity and at about 20° C.The samples were oriented with the second substrate up, i.e., face stockup, as well as release liner side up. After five minutes exposure, andafter one hour exposure, measurements were taken of the average curl atcorner of each rectangular sample from a flat surface. No appreciabledifferences in curl was noted between five minutes and one hour for thesamples of the laminated PSA construction of this invention, with thesamples displaying a radius of curvature of greater than about 14, or anedge lift of less than about three millimeters. For purposes ofreference and comparison, a radius of curvature of infinity represents aperfectly flat construct with zero curl, and a curl having a radius ofcurvature of from between infinity to 14 inches or greater is consideredto be acceptable.

The samples of the conventional PSA constructions displayed an edge liftof greater than about six millimeters, and in some cases up to about 12millimeters. The results of the lay flat tests indicate that PSAconstructions of this invention produce laminated PSA constructions thatdisplay a significant improvement in lay flat properties when comparedto conventional PSA constructions.

The improved lay flat properties achieved from using prelaminate PSAconstructions of this invention are believed to be due to the use ofambient or subactivation process temperature lamination that avoidssubstrate shrinkage that otherwise is known to occur during a heatedlamination by water loss, and that is a known cause of edge lift.

Samples of the laminated PSA construction prepared in Example 1 weretested for tensile strength at a web speed comparable to that usedduring a die cutting and matrix stripping conversion process, asmeasured crosswise across the width of the web (cross direction). Facestocks of laminated PSA constructions of this invention were found tohave a tensile strength up to about 20 percent greater than thatmeasured for the second substrate, i.e., face stock, alone. The improvedface stock tensile strength is believed due to the presence of the DL,or the second tacky layer after activation and lamination, as areinforcing material in the laminate PSA construction.

The improved tensile strength exhibited by face stocks of this inventionis important for several reasons. Such improvement facilitatesconversion of the laminated PSA construction, for example by die cuttingand matrix stripping methods as discussed above, by allowing thelaminate construction to be processed at higher web speeds withoutmatrix breaking and the like, thereby making the converting process moreefficient. Also, such an improvement allows the laminated PSAconstructions to be manufactured from lighter-weight paper stocks, e.g.,the second substrate or face stock, because of the reinforcing effectprovided to the construction by the DL, thereby reducing the rawmaterial costs associated with making the laminated PSA construction.

EXAMPLE 2 First Embodiment Prelaminate PSA Construction

A first embodiment prelaminate PSA construction was prepared by hot meltdual die process by applying a PSA layer comprising S-246 PSA to a 42pound basis weight Rhi-Liner 12 release liner, comprising a layer ofGeneral Electric 6000 silicone release material disposed thereon. A DLcomprising Uni-Rez 2623 was simultaneously applied to the PSA layer. Thecoat weight of the PSA layer was about 20 g/m.sup.2, and the coat weightof the DL was about 15 g/m.sup.2.

Samples of the Example 2 prelaminate PSA construction were activated andthen laminated to a back side of a 60 pound Krome Kote face stock,available from Champion International Corp., of Stamford, Conn. forpurposes of measuring the loop tack and 90 degree peel (20 minute dwell)for one inch wide sample sections. The substrate that was used wasstainless steel. The testing was carried out on a Instron UniversalTester at a rate of 200 millimeters per minute. Shear tests weresubsequently carried out where the dwell time in minutes of cohesionwere measured for 13 millimeter by 13 millimeter samples on stainlesssteel with a 500 gram weight. The testing was then repeated using aconventional laminated PSA construction comprising an S-246 and 60 poundKrome Kote laminate construction.

Comparison loop tack, peel, and shear test data is set forth in Table 2,where “I” refers the sample of the prelaminate PSA construction of thisinvention, and “S” refers to the standard PSA construction.

2TABLE 2 Test Value Sample Value (Force Average (in Newtons/m)(Newton/m) Loop tack I 19.2 Loop Tack I 15.1 Loop Tack I 18.9 17.7 LoopTack S 20.5 Loop Tack S 16.6 Loop Tack S 14.0 17.0 90 Degree Peel I 10.290 Degree Peel I 11.6 90 Degree Peel I 10.3 10.7 90 Degree Peel S 11.290 Degree Peel S 10.9 90 Degree Peel S 12.6 11.6 Value (Shear Average(in Minutes) (Minutes) Shear I 1509 Shear I 1059 Shear I 1358 1308 ShearS 677 Shear S 594 Shear S 556

The test data demonstrates that the laminated PSA construction ofExample 2 has superior shear properties when compared to a conventionallaminated PSA construction that does not include the activated DL. It isbelieved that such enhanced shear properties is due in part to thereinforcing effect that the DL has on the construction. This reinforcingeffect, as mentioned above with regards to improved tensile strength, isdesired as it allows for the use of lighter-weight second substrates inmanufacturing such PSA constructions.

A second embodiment prelaminate construction is formed by using adetackifying material that is capable of being chemically activated totransform the DL into a second tacky layer (as shown in FIG. 7).Suitable second embodiment detackifying materials include thosematerials that are capable of displaying adhesive properties whenexposed to chemicals such as organic or inorganic solvents, e.g., wateractivatable gums, adhesives, starches and the like, polyvinyl alcoholmixtures, polyamides, high glass transition temperature acrylates,ethylene vinyl acetate, polyacrylic acid and the like, and otherchemicals that upon exposure to water, steam, other inorganic solventsor organic solvents react to form a second tacky layer.

Second embodiment detackifying materials can be applied in the samemanner as described above for the first embodiment detackifyingmaterial. The chemical activating agent can be applied to the DL surfaceby conventional techniques, such as by spray application to a passingroll of the PSA label construction, ultrasonic wetting, condensationwetting, electrostatic spraying and the like. Alternatively, thechemical activating agent can be applied to the DL surface by roll ordie methods if precautions are taken to avoid contact between theactivated DL and a dry roll or die.

Like the first embodiment detackifying materials, it is desired that thesecond embodiment detackifying materials: (1) be good continuous filmformers; (2) be capable of completely and uniformly covering theunderlying PSA layer; and (3) have inherent properties of open tack.

An example illustrative of second embodiment prelaminate PSAconstructions, comprising chemically-activatable detackifying materialscapable of forming a second tacky layer, is as follows:

EXAMPLE 3 Second Embodiment Prelaminate PSA Construction

A second embodiment prelaminate PSA construction was prepared by hotmelt dual die process by applying a PSA layer comprising S-246 PSA to a42 pound basis weight Rhi-Liner release liner, comprising a layer ofGeneral Electric 6000 silicone release material disposed thereon. A DLcomprising a blend of 25 percent by weight Uni-Rez 2620 and 75 percentby weight Uni-Rez 2623 was simultaneously applied to the PSA layer. Thecoat weight of the PSA layer was about 20 g/m.sup.2, and the coat weightof the DL was about 10 g/m.sup.2.

A sample of the DL was moistened with a solvent mixture consisting ofabout 70 percent by weight isopropyl alcohol and 30 percent by weighttoluene. The solvent was applied from a piece of felt that had beensoaked in the solvent mixture. Within one second of being contacted withthe solvent a piece of 50 pound uncoated litho paper was hand laminatedto the solvent activated layer, and after allowing to dry for one hourat room temperature was observed to display good lay flat properties andanchorage to the face stock.

A third embodiment prelaminate PSA construction is formed by using adetackifying material that is capable of forming a continuous film thatcompletely covers the PSA layer, and that is heat activated to migrateinto the body of the PSA layer (as shown in FIG. 8) to expose anunderlying tacky PSA surface. Generally, heat-activated migration is nota preferred mechanism of activating prelaminate PSA constructionsbecause the migratable species or constituents of the detackifyingmaterial may end up contaminating the bulk of the PSA and adverselyaffecting the overall properties of the PSA. Heat-activated migrationis, however, useful in applications where it is desired that the PSAitself bond directly to the intended second substrate during lamination.

In forming third embodiment prelaminate constructions of this inventionit is desired the PSA that is selected have little or no mobile species,e.g., in the form of liquid plasticizers, liquid tackifiers, andsometimes residual monomers. In the case of rubber-based PSAs, it isdesired that the amount of plasticizing oils be significantly reduced oreven eliminated. In place of such oils, tackifying resins having asoftening point in the range of from about 20 to about 30° C. can beused. Additionally, polymers can be added to the PSA formulation for thepurpose of reducing cold flow properties to a point that the DL of suchthird embodiment will properly passivate the adhesive and render theentire construction substantially block free.

Suitable detackifying materials useful in forming such third embodimentprelaminate PSA constructions are preferably formed by applying anapproximate 10 percent by weight solids dispersion of the reactionproduct of one or more bases with one or more polar fatty acidscontaining from about 10 to about 24 carbon atoms, tall oil rosin acidsand/or olefinic polymers having acid functionality. The preferred basesare amines such as ethylenediamine. Another functional amine isN,N,N′,N′-tetramethyl ethylenediamine.

The presently preferred fatty acids are 12-hydroxystearic acid derivedfrom castor beans and marketed as Cenwax-A by Union Camp, tall oil rosinacids such as Unitol NCY manufactured and sold by Union Oil Co.,dodecanedioic acid sold by Dupont and a mixture of behenic acid, a C-22polar fatty acid, and arachidic acid, a C-20 fatty acid, sold asHystrene 9022 FLK by Humco. Detackifying materials formed by reaction ofa preferred amine with one or more of the acids and, as indicated above,are applied as an about 10 percent by weight solids dispersion in waterwith the concentration of organic amine being controlled to justcompletely react with the fatty acids.

The presently preferred compositions are about 10 percent by weightaqueous dispersion of amine salts formed by dispersing the followingfatty acid mixture of about 75 percent by weight 12-hydroxystearic acid,about 10 percent by weight tall oil rosin acid and about 15 percent byweight, dodecanedioic acid in hot water using ethylenediamine as thebase or dispersion agent. Inorganic bases, such as alkali metalhydroxides, can also be used.

The detackifying material used for forming third embodiment prelaminatePSA constructions preferably consists of a mixture of flat plate-shapedparticles and spherical particles, which particles do not display atendency to migrate into the body of the PSA. The plate-shaped particlesinterlock to form a continuous PSA covering film. This requires that theshape of the particles in the dispersion be in the form of thin platesthat can form many barrier layers when coated. It is believed that thespherical particles aid in drying and control polarity to optimizethermal migration properties into any given PSA.

The weight ratio of plate-shaped particles to spherical particles shouldbe adjusted to provide in the range of from about 5 to about 50 percentpolymer spheres on a dry weight basis of the total solids in thedispersion. At any less than about 5 percent spherical particles, thecoatings require long drying times because water molecules havedifficulty in diffusing through the layered platelets. At more thanabout 50 percent spherical particles, there is a loss in shelf life dueto the lack of enough flat platelets to form a suitable block resistantcoating.

The detackifying material is best dried at a moderate temperature duringboth the wet drying phase, as well as the final drying phase. If duringthe wet drying phase the temperature becomes too hot, the hot watersoluble fatty acid salt particles can redissolve resulting in a loss offlat plate layering. Such a loss results in a reduced shelf life. Duringthe final stages of drying, care must be taken to prevent the activationof the now heat activatable substrate. For these reasons, the dryingtemperature should be maintained at about 175° F. Since this temperatureis quite low, high velocity air impingement and pre-drying of the airare both recommended.

When using high velocity air impingement, it is important that thedetackifying material dispersions themselves behave in a thixotropicmanner. This allows them to properly flow out onto the adhesive surfacewhen coated under the conditions of shear, and to self thicken prior toair impingement to prevent them from being physically blown off of theprelaminate PSA construction.

Detackifying materials used to form third embodiments of prelaminate PSAconstructions of this invention are preferably applied by a tandemcoating method, and are applied as a dispersion. Third embodimentdetackifying materials are preferably applied using Meyer rod or reverseroll coating method, as it is believed that either such method resultsin the alignment of the plate-shaped particles in the machine direction,which is critical to obtaining non-blocking properties.

The third embodiment prelaminate PSA construction is completelynonblocking as described above, and is activated and laminated in thesame manner as described above for the first embodiment prelaminate PSAconstruction, i.e, by running the prelaminate PSA construction across anactivating means and then through a laminating means operated at ambientor subactivation process temperature conditions, as shown in FIG. 11.When the prelaminate PSA construction is routed past the activatingmeans the DL becomes heated, causing its constituents to migrate intothe underlying PSA layer body, thereby exposing the underlying tacky PSAsurface for lamination.

A feature of the third embodiment prelaminate PSA construction is thatmigration of the detackifying material constituents into the PSA layeris effected by heat only, and does not require the use of pressure toforce the constituents therein. Further, like the first embodiment, suchheat activation is accomplished in a short amount of time. In anexemplary embodiment, activation of the third embodiment DL occurs byexposing the prelaminate PSA construction to a temperature of about 150°C. for a period of about one second.

Third embodiment prelaminate PSA constructions, prepared according toprinciples of this invention, comprise a DL formed from a dispersion ofplate-shaped and spherical particles, and will be better understood byreferring to the following examples:

Component 1—Formation of Dispersion Consisting of Plate-Shaped Particles

Plate-shaped particles useful for forming a third embodiment DLdispersion are formed by combining the following fatty acids togetherand mixing until uniform: 75 percent by weight Cenwax-A from Union Camp;15 percent by weight dodecanedioic acid from Dupont of Wilmington, Del.;and ten percent by weight Unitol NCY rosin acid from Union Camp. Thefatty acid mixture is then poured out onto a siliconized liner and isallowed to solidify. Ten percent by weight of this fatty acid mixture isthen mixed with 90 percent by weight of deionized water. The mixture isthen heated to melt the fatty acid mix on top of the water.Ethylenediamine is slowly added while stirring the contents until theresultant solution just clarifies. The hot solution is then transferredto ajar that is about ¼ full of ten millimeter steel bars, covered, andplaced on a roller mill for about 24 hours. The resultant dispersion isreferred to as Component 1 and consists of flat plate-shaped particles

Component 2—Formation of Dispersion Consisting of Spherical Particles

Spherical particles useful for forming a third embodiment DL dispersionare formed by combining the following ingredients together and mixinguntil uniform: ten percent by weight AC-580, a polyethylene acrylic acidcopolymer from Allied Signal of Morristown, N.J.; 87 percent by weightdeionized water; and three percent by weight ethylenediamine. Theingredients are combined and placed into a reactor that is equipped forstirring, and are heated to a temperature of about 115° C. The heatedmixture is stirred until a uniform stable dispersion of sphericalparticles results, that is referred to as Component 2.

Component 3—Formation of EDA Dispersed Shellac

A EDA dispersed shellac for use in forming third embodiment DLdispersions is formed by combining about ten percent by weight lemonyellow No. 1 shellac from Zinsser Analytic U.K., Ltd., of Maidenhead,England; with 90 percent by weight deionized water. The mixture isheated to its boiling point, and ethylenediamine is slowly added whilestirring. The ethylenediamine is added until no more turbicidy ispresent, and the solution resembles the purple color of grape juice. Themixture is then allowed to cool to room temperature and is filtered toform a EDA dispersed shellac dispersion referred to as Component 3.

The dispersions referred to as Components 1, 2 and 3 are combined andmixed until uniform to form the detackifying material useful for formingthe DL for third embodiment prelaminate PSA constructions of thisinvention. An example third embodiment prelaminate PSA construction isprepared by using the above-described dispersion detackifying material,as follows:

EXAMPLE 4 Third Embodiment Prelaminate PSA Construction

A rubber-based hot melt PSA formulation is prepared by combining thefollowing ingredients together, melting the combined ingredients at atemperature of about 150° C., and mixing the combined ingredients untiluniform: about 13 percent by weight Pentalyn H, a rosin ester ofpentarythritol from Hercules, Inc.; 37 percent by weight Escorez 1304, aC5 resin from Exxon Chemical Co., of Houston, Tex.; 34 percent by weightKraton 1112, a SIS elastomer from Shell Chemical Co., of Houston, Tex.;five percent by weight Adtack LV, a tackifying mixture from Hercules,Inc.; nine percent by weight Unitac R-40, an ester of wood rosin fromUnion Camp; one percent by weight Ethanox 330, an antioxidant from EthylCorp., of Richmond, Va.; and one percent by weight Cyantox LDTP, anantioxidant from American Cyanamid Company of Wayne, N.J.

The resulting PSA is directly coated onto a release liner made from 42pound bias weight Rhi-Liner liner comprising a layer of GE 6000 siliconerelease material disposed thereon. The PSA thickness is in the range offrom about 18 to 20 g/m.sup.2. A ten percent solid aqueous dispersion ofthe detackifying material prepared above by combining Components 1, 2and 3 is then coated directly onto the PSA surface using a No. 8 Meyerrod. The third embodiment prelaminate PSA construction is then dried ata temperature of about 80° C. in a forced air convection oven.

A key feature of prelaminate P SA constructions prepared according toprinciples of this invention is that they display excellent nonblockingproperties, thereby allowing the construction to be placed against acontiguous backside surface of the release liner, or any other objectsurface, without adhesive interference therewith. Prelaminate PSAconstructions of this invention have been tested to determine theirminimum nonblocking temperature. An example of the block testing thatwas conducted is as follows:

Block Testing—Second Embodiment Prelaminate PSA Construction

A polyamide resin was prepared by reacting equimolar quantities of1,6-hexanediamine with Hystrene 3695 dimer acid from Humco. Theresulting mixture was dissolved at about 20 percent solids into thefollowing solvent mixture; 25 percent by weight of 2-propanol, 25percent by weight of 1-pentanol, and 50 percent by weight of 2-butanol.

A 42 pound bias weight Rhi-Liner SCK stock from Rhinelander was coatedwith G.E. 6000 silicone release formulation to a coat weight of about 1g/m.sup.2, forming a first release liner. A hot melt PSA was coated ontothe surface of the first release liner at a coat weight of about 20g/m.sup.2, and a second release liner of very low release force waslaminate to the exposed PSA to form a construction consisting of PSAbetween the two release liners. The construction was placed on an unwindof a pilot coater, the laminate was unwound, and the second releaseliner was removed to expose the active PSA surface.

The polyamide solution prepared above was coated directly onto theexposed PSA surface by direct application from a smooth steel roll in apan fed nip. The prelaminate PSA construction was dried in airfloatation ovens having three zones set for about 82° C. The resultantcoating was uniform and tack free, producing a completely detackifiedprelaminate PSA construction.

The dried coat weight of the polyamide DL was measured to be about fourg/m.sup.2.

Samples from the above-described prelaminate PSA construction consistedof four 50 millimeter by 200 millimeter strips. The strips were blocktested on a gradient temperature hot plate operated in the range of fromabout 26° C. to about 115° C. A first strip was placed on the hot platewith the DL positioned adjacent the hot plate surface and a backsidesurface of the first release liner directed up. A second strip wasplaced on top of the first strip with its DL positioned against thebackside surface of the release liner from the first strip, i.e., withsecond strip's DL facing upwardly. The strips were oriented on thegradient hot plate in their machine direction between a temperaturegradient of from about 35° C. to about 85° C.

A weight of about 22 kilograms was placed on a sufficient area the DL ofthe second strip to impose a pressure of about 40 kPa on the combinedfirst and second strip prelaminate PSA constructions. After about 24hours at the about 40 kPa, the samples were removed and observed forblocking. Blocking, for purposes of this test, is defined as the pointat which the adhesive of the second strip transfers from the releaseliner of the second strip. Blocking, at a hand delamination peel rate ofabout 25 millimeters/sec, was observed to occur between the two stripsat a temperature of about 70° C. The force needed to peel the adhesivefrom the release liner was in the range of from about 0.8 to 1.2grams/millimeter.

The result of such experiment demonstrates that prelaminate PSAconstructions of this invention are nonblocking to a minimum temperatureof at least 50° C., and in some instances to about 70° C. for 24 hoursat a pressure of about 40 kPa.

EXAMPLE 5 Repulpability of First Embodiment PSA Embodiment

Labels constructed according to Example 1 were made using a multi-diecoating technique with the polyamide layer being about 15 g/m.sup.2. Thelabels were applied to copy paper. The paper containing the label wascut into 0.5 inch by 0.5 inch squares to facilitate disintegration ofthe paper during a pulping process. The paper was disintegrated in aBritish disintegrator at about a 4% consistency level. The Samples weretaken every 5 minutes for 15 minutes. Water temperature was 25° C. andno additional chemical, such as sodium hydroxide, was added to thepaper. Handsheets were then made from the pulp using a standardhandsheet process. The handsheets were pressed, dried and at times,stained. The polyamide did not break up into small pieces, but retainedintact in the same size as it was cut.

In another study, the relative cleanliness of handsheets formed afterthe pulping operation was evaluated. In such study, paper alone wascompared to paper and film coated with S-246 adhesive and S-490adhesives with and without the polyamide layer. The results are shown inTable 3 below and confirm that the use of polyamide provide a handsheetquality that equaled that of the adhesive coated film and almost equaledthe paper alone.

3 TABLE 3 Sample Handsheet Contaminant Level, PPM Paper alone 8-15Paper+polyamide+S-246 25 Paper+polyamide+S-490 25 Film+S-246 30Film+S-490 30 Paper+S-246 1800 Paper+S-490 700

If desired, prelaminate PSA constructions of this invention can befurther treated after activation and before lamination. For example,just-activated prelaminate PSA constructions of this invention can beremoisturized after activation to restore moisture that is lost from thefirst substrate, i.e., the release liner, during the process of heatactivation. Such remoisturizing process can be effected by conventionalmeans, such as by passing the just-activated prelaminate PSAconstruction through a mist station designed to apply a mist of water tothe release liner when it passes thereby. The ability to remoisturizethe release liner after activation is desired because it helps to retainthe flexibility of the release liner, thereby helping to preventcracking and the like during removal of the release liner from thelaminated PSA construction.

Additionally, prelaminate PSA constructions of this invention can becooled between the activation and lamination processes to reduce thetemperature of the just-activated prelaminate PSA construction to belowambient process temperature or below activation temperature, i.e.,subactivation process temperature. Such cooling of just-activatedprelaminate PSA constructions of this invention may be desired whereextremely temperature sensitive face stocks are to be laminated.

Referring to FIG. 12, an alternative activating/laminating process 128for use with prelaminate PSA constructions of this inventionincorporates the step of preheating the prelaminate PSA constructionbefore activation for purposes of energy saving and the like. In anexemplary embodiment, the process 128 involves routing the prelaminatePSA construction 130 in continuous sheet form from a pay out roll 132 toan idler roll 134 positioned adjacent a backside surface 136 of a heatedplaten 138. For purposes of simplicity, the multi-layer prelaminateconstruction has been shown having a single thickness. The prelaminatePSA construction 130 is passed across the backside surface 136 to asecond idler roll 140 that routes the now preheated prelaminate PSAconstruction across a front side surface 142 of the heated platen 138.

The heated platen 138 is configured so that a leading portion 144 of thefront side surface 142 adjacent the second idler roll 140 is heated, anda terminal portion 146 of the platen opposite the leading portionincludes means 147 for transferring heat from the front side surface tothe backside surface 136. As the prelaminate PSA construction passesover the leading portion 144 of the front side surface 142 the DLbecomes heated to a desired activation temperature and then passes overthe non-heated heat transferring means 147. Heat from the now activatedprelaminate PSA construction passes through the heat transferring means147 to the backside surface 136 of the platen, causing the now activatedprelaminate PSA construction to be cooled, thereby reducing its surfacetemperature and simultaneously causing the prelaminate PSA constructionin contact with the backside surface 136 to be preheated.

Such preheating reduces the amount of energy needed at the front sidesurface to bring the prelaminate PSA construction up to the desiredactivation temperature. The use of such preheating technique is desiredbecause it reduces energy costs associated with both heating theprelaminate PSA construction to activation temperature, and cooling thejust-activated PSA construction before lamination.

The activated prelaminate PSA construction is passed from the heatedplaten 138 to laminating means 148, in the form of rollers 150, where asecond substrate 152 such as a face stock or the like is laminatedthereto under ambient or subactivation process temperature conditions.The laminated PSA construction 154 is collected on a collection roll156.

If desired, prelaminate PSA constructions of this invention can alsoundergo different treatments before being activated. For example, firstembodiment prelaminate PSA constructions may further comprise printingand the like on a surface of the DL. The DL can be printed upon afterthe prelaminate PSA construction manufacturing process at a point beforeactivation, e.g., it can be printed at any point before theactivation/lamination station 106 in FIG. 11.

Printing on the DL may be desired, e.g., in applications where thesecond substrate is a clear film, to allow viewing of the printingthrough the second substrate, or in applications where a backsidesurface of the second substrate is viewable through a clear substrate towhich the laminated PSA construction is applied. It is, therefore, to beunderstood that prelaminate PSA constructions of this invention mayinclude a DL that includes printing and the like thereon.

First and second embodiment prelaminate PSA constructions of thisinvention can also comprise a tinted DL. In certain applications, e.g.,where the second substrate is in the form of a clear film, it may bedesirable to tint the DL to avoid having to use a tinted secondsubstrate, or to avoid having to tint the PSA layer as the use of tintin the PSA layer may adversely affect its adhesive properties. It is,therefore, to be understood that prelaminate PSA constructions mayinclude a DL that includes tinting.

Additionally, before the step of activating first and second embodimentprelaminate PSA constructions it may be desirable to die cut and matrixstrip a portion of the DL and PSA layer from the release liner. Asillustrated in FIG. 13, first, second and third prelaminate PSAconstructions of this invention 170, comprising a release liner 172having a coating of release material 174 disposed thereon, a PSA layer176 on the coating of release material, and a DL 178 on the PSA layer,can be configured having one or more adhesion-free zones 180. Theadhesion-free zones 180 are defined by surrounding PSA and DLs andextend to the coating of release material of the prelaminate PSAconstruction. The adhesion-free zones can extend lengthwise in a machinedirection and/or widthwise along the prelaminate PSA construction todefine islands of DLs and PSA layers. The formation of suchadhesive-free zones is desired to prevent gumming of the PSA afteractivation that can interfere with the lamination process and makeseparation of the laminated PSA construction from the release linerdifficult.

Referring to FIG. 14, an exemplary laminated PSA construction 182 basedon first and second embodiment activated prelaminate PSA construction(see FIG. 7) comprises a release liner 184 having a coating of releasematerial 186 disposed thereon, a PSA layer 188 disposed onto the coatingof release material, and a DL 190 disposed on the surface of the PSAlayer. A second substrate 194 is laminated to a surface of the DL 190.The second substrate 194, DL 190 and PSA layer 188 are permanentlyjoined together so that they can be removed together from the releaseliner 184. Removal of the release liner from the laminated constructionexposes the PSA layer for adhering the laminated construction to adesired article or object.

Referring to FIG. 15, an exemplary third embodiment laminated PSAconstruction 196, based on a third embodiment activated prelaminate PSAconstruction (see FIG. 8) comprises a release liner 198 having a coatingof release material 200 disposed thereon, a PSA layer 202 disposed onthe coating of release material, and detackifying material constituents204 that have migrated into the body of the PSA layer. A secondsubstrate 208 is laminated to a surface of the PSA layer 202. The secondsubstrate 208 and PSA layer 202 are permanently joined together so thatthey can be removed together from the release liner 198. Removal of therelease liner from the laminated construction exposes the PSA layer foradhering the laminated construction to a desired article or object.

Prelaminate PSA constructions, prepared according to principles of thisinvention, can be used as a means for not only subsequent lamination ofsecond substrates such as face stocks and the like, but can be used as avehicle for enclosing a variety of different objects, articles ordevices. For example, such objects can be incorporated into theprelaminate PSA construction during the manufacturing process betweenthe activation and lamination steps, during the open tack time of thejust-activated prelaminate PSA construction.

An example of devices than can be incorporated into laminated PSAconstructions of this invention include electronic article surveillance(EAS) devices, such as acoustic-magnetic, electromagnetic, andradio-frequency-type magnetic circuits, and electronic bar code labelsand associated systems, can be incorporated into the laminated PSAconstruction for subsequent attachment to a particular article or objectby removal of the release liner for purposes of monitoring thewhereabouts of the particular good, e.g., to an article of clothingplaced for sale within a store.

Referring again to FIG. 14, with respect to a laminated PSA constructionbased on first and second embodiment prelaminate PSA constrictions ofthis invention, an object 192 can be placed onto or embedded into thejust-activated DL 190 before the step of laminating. The secondsubstrate 194 is laminated onto the DL 190, thereby encasing the object192 therebetween.

Referring again to FIG. 15, with respect to a laminated PSA constructionbased on third embodiment prelaminate PSA constructions of thisinvention, an object 206 can be placed onto or embedded into the PSAlayer 202. The second substrate 208 is laminated onto the PSA layer,thereby encasing the object 206 therebetween.

In forming laminated PSA constructions that include such objects, theobjects are inserted after the prelaminate PSA construction is activatedduring the open tack time period. For example, with respect to first andsecond embodiment prelaminate PSA constructions, this can be done at theactivation/lamination station in FIG. 11 at a point before lamination.

It is to be understood that such objects can be placed on top of the DL,can be embedded into the DL, or can be disposed within a preformedcavity within the DL. It is desired that the object be generallycoplanar with the activated surface for lamination to thereby notproject into the laminated second substrate and not adversely affectadhesion with the DL.

The type of second substrate that can be used to encase the object ineach of the above-described embodiments depends on the particularconstruction application and on the type of object that is used. Forexample, if the object is of a slim design and can function, in the caseof a functional device, while placed on top of or embedded in the DL orPSA layer, then the second substrate may be in the form of a web orsheet stock. If, for example, the object is not of a slim design orrequires an area of unrestricted space for proper operation, in the caseof a functional device, the second substrate may be in the form of ahousing that is designed to both adhere to the DL or PSA layer and coveran area around the object. In either case, the second substrate may bedeformed or shaped to accommodate placement of the object within theconstruction.

Although limited embodiments of prelaminate PSA constructions andmethods for making the same according to principles this invention havebeen described herein, many modifications and variations will beapparent to those skilled in the art. Accordingly, it is to beunderstood that, within the scope of the appended claims, prelaminatePSA constructions of this invention may be prepared other than asspecifically described herein.

1. A method for forming a pressure-sensitive adhesive constructioncomprising the steps of: a) depositing a layer of pressure-sensitiveadhesive material onto a coating or release material that is disposed ona surface of a first flexible substrate; and b) applying a layer ofcontinuous film forming material onto a surface of thepressure-sensitive adhesive layer to render the pressure sensitiveadhesive construction completely nonblocking, the continuous filmforming material being applied to the pressure-sensitive adhesive atsubstantially the same time that the pressure-sensitive adhesivematerial is deposited.
 2. The method as recited in claim 1 wherein thelayer of continuous film forming material is applied in the form of ahot melt or an emulsion.
 3. The method as recited in claim 1 wherein thelayer of continuous film forming material is applied in the form of ahot melt and has a hot melt viscosity that is within a factor of abouttwo times a hot melt viscosity for the pressure sensitive adhesive. 4.The method as recited in claim 1 further comprising the step ofactivating the continuous film forming material to form a tacky surfaceindependent of the pressure sensitive adhesive for supporting adhesionto a second substrate.
 5. The method as recited in claim 4 wherein thestep of activating is achieved by heat.
 6. The method as recited inclaim 4 wherein the activated continuous film is laminated to a secondsubstrate at a temperature of less than about 100° C.
 7. The method asrecited in claim 4 wherein the continuous film forming material isactivated for lamination in less than about five seconds.
 8. Apressure-sensitive laminate construction prepared according to themethod of claim
 1. 9. A method for forming a laminatedpressure-sensitive adhesive construction comprising the steps of: a)depositing a layer of pressure-sensitive adhesive material onto acoating or release material that is disposed on a surface of a firstflexible substrate; and b) applying a detackifying material onto asurface of the pressure-sensitive adhesive layer to occlude thepressure-sensitive adhesive layer and form a nonblocking detackifiedpressure-sensitive adhesive construction, the detackifying materialbeing heat activatable; c) heating the detackifying material to anactivation temperature to provide a tacky surface independent of thepressure-sensitive adhesive for lamination; and d) laminating a secondsubstrate to the tacky surface of the detackifying material at atemperature less than about 100° C. to form a laminatedpressure-sensitive adhesive construction having the second substrate;wherein the step of depositing and applying occur at substantially thesame time.
 10. The method as recited in claim 9 wherein during the stepof heating, the tacky surface has an open tack time in the range of from0.25 to 5 seconds.
 11. The method as recited in claim 9 wherein beforethe step of heating, the detackifying material is heat treated byheating to a temperature below an activation temperature.
 12. The methodas recited in claim 9 further comprising, between the step of applyingand heating, the steps of: collecting the detackified pressure-sensitiveadhesive construction by placing the detackified pressure-sensitiveadhesive adjacent to a contiguous surface of the first flexiblesubstrate; and removing the collected detackified pressure-sensitiveadhesive from the contiguous first flexible substrate surface.
 13. Apressure-sensitive adhesive prepared according to the method recited inclaim
 9. 14. A method for forming a laminated pressure-sensitiveadhesive construction comprising the steps of: a) heating a detackifiedprelaminate pressure-sensitive adhesive construction to an activationtemperature to form a tacky surface for lamination, saidpressure-sensitive adhesive construction comprising: a first substratecomprising a coating of release material disposed thereon; apressure-sensitive adhesive disposed on the coating of release material;and a continuous film layer disposed on a surface of thepressure-sensitive adhesive to occlude the pressure-sensitive adhesivelayer, the continuous film layer being, in combination with thepressure-sensitive adhesive, self supporting and forming a tacky surfaceindependent of the pressure-sensitive adhesive upon heating to anactivation temperature; and b) laminating a second substrate to thetacky surface of the activated continuous film layer to form a laminatedpressure-sensitive adhesive construction; wherein the continuous filmlayer is applied to the pressure-sensitive adhesive while thepressure-sensitive adhesive is not fully cured.
 15. The method asrecited in claim 14 wherein the continuous film layer forms a bond withthe pressure-sensitive adhesive that is stronger than a bond formed withthe second substrate to facilitate preferential removal of the secondsubstrate from the continuous film layer and pressure sensitive adhesiveduring paper reclamation.
 16. The method as recited in claim 14 whereinduring the step of heating, the tacky surface is formed in less thanabout five seconds.
 17. The method as recited in claim 14 wherein thestep of laminating takes place in the range of from 0.25 to 5 secondsafter the step of heating.
 18. The method as recited in claim 14 furthercomprising between the steps of heating and laminating, placing anobject on the tacky surface.